How can i stop the auto update?

hello everyone. I am a new user of windows 8. how can i stop the auto update. every time i m going to removing the option of auto update a dialogue box is appearing and telling that permission of the administrator is needed. i m frustrated as my data usage is increasing possibly due to this auto update.... 160 megabyte per hour...while i am only checking mail......can u believe it. plz someone help me by reading it carefully.